Design of Beam Shaping Assembly for an Accelerator-driven BNCT System in Nagoya University

Authors:   Uritani A., Menjo Y., Watanabe K., Yamazaki A., Kiyanagi Y., Tsuchida K.
Journal: Proceedings of the International Conference on Neutron Optics
https://dx.doi.org/10.7566/jpscp.22.011002
Abstract: An accelerator-driven compact neutron source for boron neutron capture therapy (BNCT) has been developed in Nagoya University since 2013. A Dynamitron accelerator and a Li target are used to generate neutrons. The 7Li(p, n)7Be nuclear reaction produces neutrons. Since the generated neutrons have considerably high energy, up to one MeV, it is necessary to lower the neutron energy to an epithermal region that is suitable for BNCT. In this work, we have designed a beam shaping assembly (BSA) that lowers the neutron energy and makes beam-like neutrons. The BSA consists of a MgF2 moderator, a lead reflector, a radiation shield and a neutron collimator. The PHITS (Ver.2.66) code has been used to simulate the neutron transport in the BSA. This paper mainly describes two issues. One is the optimization of the shape of the BSA, mainly the moderator, and the other is the dependence of the simulation results on the nuclear data libraries, JENDL-4.0 and ENDF/B-VII.1.